These days, there is a need for analysis and evaluation of the impact made by a specific event designated by the user, such as an incident or an advertising campaign, on a subject of interest, for the purpose of marketing, public opinion survey, or the like. For example, let us assume that a user is interested in, as an analysis subject, “dieting effect of product X”, and an incident relating to the product X has occurred (e.g., a scandal involving the manufacturer of the product X). In this case, there is a need for measurement by which what impact was made by the incident on a public image and evaluation of the analysis subject “dieting effect of product X” after the incident.
As existing methods for meeting such need, there are conventional technologies using an “assessment information extraction technique”. Non-Patent Documents 1 and 2 disclose examples of “assessment information extraction technique”. Here, “assessment information extraction technique” refers to a technology for extracting, from a document, an expression (hereinafter, referred to as “assessment information”) indicating an evaluation (including a value judgment) described in the document and made by the author of the document. Furthermore, methods for grouping extracted assessment information into expressions indicating a positive evaluation, expressions indicating a neutral evaluation, and expressions indicating a negative evaluation have been published as the assessment information extraction technique.
Additionally, for example, Non-Patent Documents 3 and 4 disclose techniques in which the assessment information extraction technique disclosed in Non-Patent Documents 1 and 2 above is applied to a document set provided with their origination dates, such as blogs on the Internet. According to the techniques disclosed in Non-Patent Documents 3 and 4, assessment information indicating a positive evaluation and assessment information indicating a negative evaluation that appear in the document set are extracted, then the number of appearances of these pieces of assessment information for each origination date is counted, and the temporal transition of the number of appearances is output as a graph or the like.
For example, the user can apply the techniques disclosed in Non-Patent Documents 3 and 4 above to a document containing a description regarding an analysis subject (hereinafter, referred to as an “analysis subject document”), thus visualizing the change of the number of appearances of the assessment information for the analysis subject. Then, the user can analyze the visualized change of the number of appearances of the assessment information, thus carrying out investigation as to what impact that the event of interest has on the public evaluation on a given analysis subject.
Furthermore, if the user knows the date of the event of interest, the user can understand the increase and decrease in the amount of the positive assessment information or the negative assessment information contained in the analysis subject documents after that date, from the change in the number of appearances of the visualized assessment information. Specifically, to put it simply, if the amount of the positive assessment information has increased after the event, the user can judge that the evaluation on the analysis subject has changed in a favorable direction by that event. Conversely, if the amount of the negative assessment information has increased after the event, the user can judge that the evaluation on the analysis subject has changed in an unfavorable direction by that event. Additionally, the amount of increase in the positive assessment information or the negative assessment information indicates the magnitude of impact of the event. Thus, the user can judge, for example, the magnitude of impact and the direction of impact of the event, using the techniques disclosed in Non-Patent Documents 3 and 4.